Apparatus and method for anterior spinal stabilization

ABSTRACT

A spinal fixation device for stabilizing one or more segments of the human spine and for preventing the dislodgement of intervertebral spinal fusion implants, which remains permanently fixated once applied. The spinal fixation device of the present invention comprises of a staple member made of material appropriate for human surgical implantation which is of sufficient length to span the disc space between two adjacent vertebrae and to engage, via essentially perpendicular extending projections, the vertebrae adjacent to that disc space. A portion of the staple of the spinal fixation device interdigitates with an already implanted intervertebral spinal fusion implant which itself spans the disc space to engage the adjacent vertebrae, and the spinal fixation deice is bound to the spinal fusion implant by a locking means. The spinal fixation device of the present invention is of great utility in restraining the vertebrae adjacent to the spinal fusion implant from moving apart as the spine is extended and also serves as an anchor for a multi-segmental spinal alignment means for aligning more that one segment of the spine.

[0001] This is a continuation of application Ser. No. 10/105,773, filedMar. 25, 2002; which is a continuation of application Ser. No.09/563,705, filed May 2, 2000, now U.S. Pat. No. 6,364,880; which is acontinuation of application Ser. No. 09/126,585, filed Jul. 31, 1998,now U.S. Pat. No. 6,136,001; which is a continuation of application Ser.No. 08/926,334, filed Sep. 5, 1997, now U.S. Pat. No. 6,120,503; whichis a continuation of Ser. No. 08/589,787, filed Jan. 22, 1996, nowabandoned; which is a continuation of 08/219,626, filed Mar. 28, 1994,now abandoned; all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to surgical interbody fixation devices andin particular to a surgically implantable device for the stabilizationof adjacent vertebrae of the human spine undergoing spinal arthrodesisand for the prevention of the dislodgement of spinal fusion implantsused in the fusion process.

[0004] 2. Description of the Related Art

[0005] When a segment of the human spine degenerates, or otherwisebecomes diseased, it may become necessary to surgically remove theaffected disc of that segment, and to replace it with bone for thepurpose of obtaining a spinal fusion by which to restore more normal,pre-morbid, spatial relations, and to provide for enhanced stabilityacross that segment. Performing such surgery of the spine from ananterior (front) approach offers the great advantage of avoiding thespinal cord, dural sac, and nerve roots. Unfortunately, in entering thedisc space anteriorly a very important band-like structure called theanterior longitudinal ligament, is violated. This structurephysiologically acts as a significant restraint resisting the anteriordisplacement of the disc itself and acting as a tension band binding thefront portions of the vertebrae so as to limit spinal hyperextension.

[0006] Historically, various devices have been utilized in an attempt tocompensate for the loss of this important stabilizing structure. Thesedevices have assumed the form of blocks, bars, cables, or somecombination thereof, and are bound to the vertebrae by screws, staples,bolts, or some combination thereof. The earliest teachings are of ametal plate attached to adjacent vertebrae with wood-type screws. Dwyerteaches the use of a staple-screw combination. Brantigan U.S. Pat. No.4,743,256 issued on May 10, 1988, teaches the use of a block inserted toreplace the disc, affixed to a plate then screwed to the vertebrae aboveand below. Raezian U.S. Pat. No. 4,401,112 issued on Aug. 30, 1993,teaches the use of a turnbuckle affixed to an elongated staple such thatat least one entire vertebral body is removed, the turnbuckle portion isplaced within the spine, and the staple extends both above and below theturnbuckle and engages the adjacent vertebrae to the one removed.

[0007] Unfortunately, both staples and screws have quite predictablydemonstrated the propensity to back out from the vertebrae. This isquite understandable as any motion, either micro or macro, tends tostress the interface of the metallic implant to the bone, and in doingso causes the bone to relieve the high stress upon it by resorbing andmoving away from the metal. This entropic change is universally from themore tightened and thus well-fixated state, to the less tightened andless fixated state. For a staple, this is specifically from the morecompressed and engaged state, to the less compressed and disengagedstate. Similarly, screws in such a dynamic system loosen and back out.

[0008] The potential consequences of such loosening and consequentbacking out of the hardware from the anterior aspect of the vertebralcolumn may easily be catastrophic. Because of the proximity of the greatvessels, aortic erosions and perforations of the vena cava and iliacvessels have usually occurred with unfortunate regularity and haveusually resulted in death.

[0009] Therefore, the need exists for a device which is effective inrestoring stability to a segment of the spine such as, but not limitedto, the anterior aspect of the human spine and which will without dangerremain permanently fixated once applied.

SUMMARY OF THE INVENTION

[0010] The present invention is directed to a spinal fixation device forstabilizing a segment of the human spine and for preventing thedislodgement of intervertebral spinal fusion implants, which remainspermanently fixated to the spine once applied. The spinal fixationdevice of the present invention comprises a staple member made of amaterial appropriate for human surgical implantation and which is ofsufficient length to span the disc space between two adjacent vertebrae.The staple member engages, via essentially perpendicular extendingprojections, the vertebrae adjacent to that disc space. The projectionsare sharpened and pointed so as to facilitate their insertion into thevertebrae and are segmented or ratcheted to prevent the staple memberfrom disengaging and backing out once inserted.

[0011] In the preferred embodiment of the spinal fixation device of thepresent invention, a portion of the staple member interdigitates with analready implanted intervertebral spinal fusion implant and the staplemember is bound to the spinal fusion implant by a locking mechanism suchas a screw with a locking thread pattern. The anchoring of the staplemember via a locking mechanism to a spinal fusion implant protects thepatient from the danger of the staple member itself disengaging andbacking out. Further, if the spinal fusion implant is externallythreaded, such as the spinal fusion implant taught by Michelson, U.S.Pat. No. 5,015,247 issued on May 14, 1991, then the staple member couldonly back out if the spinal fusion implant were free to rotate. However,the rotation of the spinal fusion implant in this instance is blocked byits connection to the staple member which is fixated across the discspace in such a way as to be incapable of rotation. Thus, the staplemember is made safe against dislodgement by attachment to the spinalfusion implant and the stability of the spinal fusion implant is assuredas it is also stabilized by the staple member and each works inconnection with the other to remove the only remaining degree of freedomthat would allow for the disengagement of either.

[0012] The spinal fixation device of the present invention is broadlyapplicable to the anterior, posterior and lateral aspects of the spinalcolumn, be it the cervical, thoracic or lumbar area. In particular, theuse of a staple member spanning the disc space and engaging the adjacentvertebrae which is applied to the anterior aspect of the spine is ofgreat utility in restraining those vertebral bodies from moving apart asthe spine is extended and thus is effective in replacing the anteriorlongitudinal ligament of the patient.

[0013] The spinal fixation device of the present invention provides theadvantage of facilitating cross vertebral bony bridging (fusion viaimmobilization) which when achieved relieves all of the forces on theinserted spinal fusion implants. The spinal fixation device of thepresent invention may be coated with materials to promote bone fusionand thus promote the incorporation and ultimate entombment of the spinalfixation device into the bone fusion mass. The use of a bone fusionpromoting material results in a speedier vertebra to vertebra fusion asbone may grow along the coated spinal fixation device bridging the twovertebrae so that the spinal fixation device acts as a trellis andsupplies essential chemical elements to facilitate the bone fusionprocess.

[0014] Another advantage provided by the spinal fixation device of thepresent invention is that as it is inserted it compresses the adjacentvertebrae together, thus increasing the compressive load on the spinalfusion implants or implants within the disc space, such compressionbeing beneficial to fusion and further stabilizing the spinal fusionimplants.

[0015] A further advantage of the spinal fixation device of the presentinvention is that it may be used as an anchor such that a multiplicityof spinal fixation devices may then be interconnected via a cable, rod,bar, or plate, so as to achieve or maintain a multi-segmental spinalalignment.

[0016] Alternatively, the spinal fixation device of the presentinvention could be made of resorbable materials, such as bio-compatibleresorbable plastics, that resorb at an appropriate rate such that oncethe spinal fixation device is no longer needed (i.e. when spinal fusionis complete) the body would resorb the spinal fixation device. Thespinal fixation device could be only in part resorbable such that theprojections of the staple member would be non-resorbable and wouldremain incarcerated in the vertebrae and sealed off once the resorbableportion of the staple is resorbed by the body.

[0017] As a further alternative, the spinal fixation device of thepresent invention could be made wholly of in part of ceramic and moreparticularly made of or coated with a ceramic such as hydroxyapatitethat would actively participate in the fusion process.

OBJECTS OF THE PRESENT INVENTION

[0018] It is an object of the present invention to provide a spinalfixation device having a staple member spanning the disc space andengaging two adjacent vertebrae of the spine to restrain the vertebraefrom moving apart as the spine is extended;

[0019] It is an another object of the present invention to provide aspinal fixation device that is effective in replacing the function ofthe anterior longitudinal ligament of a patient;

[0020] It is a further object of the present invention to provide ameans for protecting the patient from the danger of the spinal fixationdevice itself disengaging and backing out by its being anchored to anintervertebral spinal fusion implant;

[0021] It is still another object of the present invention to provide aspinal fixation device that blocks the rotation of an intervertebralspinal fusion implant by its connection to the staple member which isfixated across the disc space in such a way as to be incapable ofrotation thereby preventing the spinal fusion implant from backing out;

[0022] It is yet another object of the present invention to provide aspinal fixation device that is broadly applicable to the anterior aspectof the spinal column, be it the cervical, thoracic or lumbar area;

[0023] It is another object of the present invention to provide a spinalfixation device which may be applied longitudinally at any point aboutthe circumference of the anterior aspect of the spine;

[0024] It is also another object of the present invention to provide aspinal fixation device that stabilizes a surgically implanted spinalfusion implant and works in connection with the spinal fusion implant toprevent disengagement of either;

[0025] It is another object of the present invention to provide a spinalfixation device that achieves cross vertebral bony bridging (fusion)which ultimately relieves all of the forces on inter-vertebral spinalfusion implants inserted within the disc space between two adjacentvertebrae, and provides for a permanently good result;

[0026] It is another object of the present invention to provide a spinalfixation device that serves as an anchor, such that a multiplicity ofthese anchors may then be interconnected via a cable, rod, bar, orplate, so as to achieve or maintain a multi-segmental spinal alignment;and

[0027] It is a further object of the present invention to provide aspinal fixation device that directly participates in the bony bridgingof two adjacent vertebrae and participates in the spinal fusion processacross those vertebrae.

[0028] These and other objects of the present invention will becomeapparent from a review of the accompanying drawings and the detaileddescription of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a perspective side view of a segment of the spinalcolumn having two spinal fusion implants shown partially in hidden lineinserted across the disc space between two adjacent vertebrae with eachspinal fusion implant having a spinal fixation device of the presentinvention shown partially in hidden line secured thereto, spanningacross the disc space and inserted into the vertebrae.

[0030]FIG. 2 is a perspective side view of a segment of the spinalcolumn having two spinal fusion implants inserted across the disc spacebetween two adjacent vertebrae.

[0031]FIG. 3 is an elevational side view of a cylindrical threadedspinal fusion implant.

[0032]FIG. 4 is an end view of the cylindrical threaded spinal fusionimplant along lines 4-4 of FIG. 3.

[0033]FIG. 5 is a perspective side view of a segment of the spinalcolumn having two non-threaded spinal fusion implants with externalratchetings, shown in hidden line, inserted across the disc spacebetween two adjacent vertebrae with each spinal fusion implant having aspinal fixation device of the present invention, shown partially inhidden line, coupled thereto, spanning across the disc space andinserted into the vertebrae.

[0034]FIG. 6 is a perspective side view of a segment of the spinalcolumn having two spinal fusion implants having truncated sides withexternal ratchetings shown in hidden line inserted across the disc spacebetween two adjacent vertebrae with each spinal fusion implant having aspinal fixation device of the present invention shown partially inhidden line coupled thereto, spanning across the disc space and insertedinto the vertebrae.

[0035]FIG. 7 is a perspective side view of a segment of the spinalcolumn having two spinal fusion implants having a knurled externalsurface shown in hidden line inserted across the disc space between twoadjacent vertebrae with each spinal fusion implant having a spinalfixation device of the present invention shown partially in hidden linecoupled thereto, spanning across the disc space and inserted into thevertebrae.

[0036]FIG. 8 is a top plan view of the spinal fixation device of thepresent invention.

[0037]FIG. 9 is a side view of the spinal fixation device of the presentinvention along lines 9-9 of FIG. 8.

[0038]FIG. 10 is a cross sectional view taken along lines 10-10 of FIG.8 showing the top member of the spinal fixation device of the presentinvention.

[0039]FIG. 11 is an enlarged fragmentary perspective side view of aprojection of the spinal fixation device of the present invention takenalong line 11 of FIG. 9.

[0040]FIG. 12 is a cross sectional view of the spinal fixation device ofthe present invention inserted into the vertebrae and secured to thespinal fusion implant with the arrows showing the forces exerted, therotational axis and the longitudinal axis of the spinal fusion implant.

[0041]FIG. 13A is a cross sectional view along line 13-13 of FIG. 9 ofthe preferred embodiment of the projections of the present invention.

[0042]FIGS. 13B, 13C, 13D, 13E, and 13F are cross sectional views takenalong line 13-13 of FIG. 9 showing alternative embodiments of theprojections of the spinal fixation device of the present invention.

[0043]FIG. 14 is an enlarged elevational side view of the locking screwused to secure the spinal fixation device of the present invention to aspinal fusion implant.

[0044]FIG. 15A is a cross sectional view of a securing means for lockingthe locking screw of the present invention.

[0045]FIG. 15B is a cross sectional view of a first alternativeembodiment of the securing means for locking the locking screw of thepresent invention.

[0046]FIG. 15C is a cross sectional view of a second alternativeembodiment of the securing means for locking the locking screw of thepresent invention.

[0047]FIG. 16A is a perspective side view of the instrumentation usedfor driving the spinal fixation device of the present invention into thevertebrae.

[0048]FIG. 16B is a perspective side view of a first alternativeembodiment of the instrumentation used for driving the spinal fixationdevice of the present invention into the vertebrae.

[0049]FIG. 17A is a perspective side view of an alignment rod used toalign the spinal fixation device of the present invention.

[0050]FIG. 17B is a perspective side view of an alternative embodimentof the alignment rod having splines used to align the spinal fixationdevice of the present invention.

[0051]FIG. 18 is a front perspective view of the drill templateinstrument.

[0052]FIG. 19 is a perspective side view of the alignment rod attachedto a spinal fusion implant inserted in the disc space between twoadjacent vertebrae.

[0053]FIG. 20 illustrates the step of drilling guide holes in thevertebrae adjacent to the spinal fusion implant with the drill templateinstrument of FIG. 18.

[0054]FIG. 21 illustrates a step of the method of inserting the spinalfixation device of the present invention with the alignment rod attachedto the spinal fusion implant and the spinal fixation device placed onthe driver instrumentation.

[0055]FIG. 22 illustrates a step of the short method of inserting thespinal fixation device of the present invention with the driverinstrument engaging the splined alignment rod and a hammer for applyingan impaction force and driving the driver instrument.

[0056]FIG. 22A is an enlarged fragmentary view of a projection beinginserted into an insertion hole drilled within a vertebra shown in crosssection taken along line 22A of FIG. 21.

[0057]FIG. 23 illustrates another step of the method of inserting thespinal fixation device of the present invention in which the spinalfixation device has been driven into the vertebrae and the driverinstrumentation has been removed.

[0058]FIG. 24 illustrates another step of the method of inserting thespinal fixation device of the present invention with the splinedalignment rod being removed from the spinal fusion implant and thelocking screw being inserted and secured the spinal fixation device tothe spinal fusion implant.

[0059]FIG. 25 is a top plan view of a first alternative embodiment ofthe spinal fixation device of the present invention.

[0060]FIG. 26 is a top plan view of a second alternative embodiment ofthe spinal fixation device of the present invention.

[0061]FIG. 27 is a perspective side view of a third alternativeembodiment of the spinal fixation device of the present inventioncoupled to two spinal fusion implants and inserted in adjacent vertebraeof the spinal column.

[0062]FIG. 28 is a top plan view of a fourth alternative embodiment ofthe spinal fixation device of the present invention inserted into thevertebrae of the spinal column having a spinal fusion implant insertedin the disc space.

[0063]FIG. 29 is a top plan view of a fifth alternative embodiment ofthe spinal fixation device of the present invention inserted into thevertebrae of the spinal column having a spinal fusion implant insertedin the disc space.

[0064]FIG. 30 is a perspective bottom view of the fourth alternativeembodiment of the spinal fixation device of the present invention.

[0065]FIG. 31 is a cross sectional view along lines 31-31 of FIG. 29showing the fifth alternative embodiment of the spinal fixation deviceof the present invention inserted into the adjacent vertebrae andcoupled to a spinal fusion implant.

[0066]FIG. 32 is a cross sectional view along lines 32-32 of FIG. 29showing the projections of the fifth alternative embodiment of thepresent invention with respect to a spinal fusion implant insertedwithin the disc space.

[0067]FIG. 33 is a cross sectional view of a spinal fixation device ofthe present invention engaging two adjacent vertebrae and being attachedto a spinal fusion implant, shown being used as an anchor for amulti-segmental spinal alignment means.

[0068]FIG. 34 is an enlarged elevational side view of a threaded postused to connect the spinal fixation device of the present invention to amulti-segmental spinal alignment means.

[0069]FIG. 35 is an exploded perspective view of a sixth alternativeembodiment of the spinal fixation device of the present invention havingindependent projection members that are screws.

DETAILED DESCRIPTION OF THE DRAWINGS

[0070] Referring to FIGS. 1 and 2, two identical spinal fixation devicesof the present invention, each being generally referred to by thenumerals 10 and 11, respectively, are shown inserted into two vertebraeV adjacent to a disc D of a segment of the human spine. Each spinalfixation device 10 and 11 is shown coupled to identical spinal fusionimplants 40 and 41 that have been surgically implanted in the disc spacebetween adjacent vertebrae V. In this manner, the spinal fixationdevices 10 and 11 stabilize a segment of the spine, prevent thedislodgement of the spinal fusion implant 40, and remain permanentlyfixated to the spine once applied. The spinal fixation devices 10 and 11are identical such that the description of one is equally applicable tothe other. Thus, the description that follows will be directed to spinalfixation device 10.

[0071] Referring to FIGS. 3-4, the spinal fusion implant 40 such as, butnot limited to, the spinal fusion implant described by Michelson, U.S.Pat. No. 5,015,247 issued on May 14, 1991, is shown. The spinal fusionimplant 40 is cylindrical in shape and has external threads 42 at itsouter perimeter for engaging the bone of the vertebrae V adjacent to thedisc D. The spinal fusion implant 40 has a trailing end 43 having adepression 44 and a threaded aperture 45 for engaging a portion of thespinal fixation device 10 and also for engaging a portion of aninstrument used to insert the spinal fixation device 10 into thevertebrae V.

[0072] Referring to FIGS. 5-7, it is appreciated that the spinalfixation devices 10 and 11 of the present invention are not limited inuse with a threaded spinal fusion implant 40 and 41, but may be usedwith different types of spinal fusion implants. For example, the spinalfixation devices 10 and 11 may be coupled to spinal fusion implants 40 aand 41 a, respectively, each having external ratchetings 42 a instead ofexternal threads 42 as shown in FIG. 5. Alternatively, the spinalfixation devices 10 and 11 may be coupled to spinal fusion implants 40 band 41 b, respectively, each having a partially cylindrical shape withat least one truncated side 47 as shown in FIG. 6. As a furtheralternative, the spinal fixation devices 10 and 11 may be coupled tospinal fusion implants 40 c and 41 c, respectively, each having aknurled external surface 48 as shown in FIG. 7. It is also appreciatedthat the spinal fixation devices may be used with a variety of otherbone fusion implants without departing from the scope of the presentinvention.

[0073] Referring to FIGS. 8-9, in the preferred embodiment, the spinalfixation device 10 of the present invention comprises a staple member 12having a substantially planar top member 14 which is of sufficientlength to span one intervertebral disc D and to engage, via a pluralityof essentially perpendicular extending projections 16 and 17, thevertebrae V adjacent to that disc D. The top member 14 has a centralopening 18 within a concentric, countersunk recess 19 for receivingtherethrough a screw or similar coupling means for coupling the spinalfixation device 10 to the spinal fusion implant 40. The top member 14has an upper surface 20 having a pair of openings 22 a and 22 b forreceiving the posts 88 a and 88 b of a driving instrument 80 which isdescribed in greater detail below in reference to FIGS. 16A and 16B.

[0074] Referring to FIG. 10, a cross sectional view of the top member 14is shown. In the preferred embodiment, the top member 14 is generallytriangularly shaped and is radiused along curved side 24 and straightside 26. The curved side 24 of the top member 14 is radiused at itsupper edge 25 and at the upper edge 27 of straight side 26 to conform tothe external curvature of the vertebrae V. In this manner, smoothsurfaces are created at the upper edges 25 and 27 of the top member 14that are contoured to the shape of the external curvature of thevertebrae V when the staple member 12 is in place. The smooth contouredsurface of the upper edges 25 and 27 of the top member 14 prevent aorticerosions and perforations of the vessels proximate the vertebral columnsuch as the vena cava and the iliac vessels which might otherwise resultfrom friction.

[0075] In the preferred embodiment of the spinal fixation device 10, thetop member 14 has a width ranging from 6.0 mm to 28.0 mm, with 10.0 mmbeing the preferred width, and having a thickness in the range of 2.0 mmto 4.0 mm, with 3.0 mm being the preferred thickness. The staple member12 is made of material appropriate for human surgical implantationincluding all surgically appropriate metals such as but not limited to,titanium, titanium alloy, chrome molybidium alloys, stainless steel; ornon-metallic materials including permanent or resorbable substances orcomposites, carbon fiber materials, resins, plastics, ceramics orothers.

[0076] Further, the staple member 12 of the present invention may betreated with, or even composed of, materials known to participate in orpromote in the fusion process or bone growth. The spinal fixation device10 may be coated with materials to promote bone fusion and thus promotethe incorporation and ultimate entombment of the spinal fixation device10 into the bone fusion mass. The use of a bone fusion promotingmaterial such as, but not limited to hydroxyapatite, hydroxyapatitetricalcium phosphate or bone morphogenic protein, results in a speediervertebra V to vertebra V fusion as bone may grow along the coated spinalfixation device 10 bridging the two vertebrae V so that the spinalfixation device 10 acts as a trellis and supplies essential chemicalelements to facilitate the bone fusion process.

[0077] Referring again to FIG. 9, the projections 16 and 17 arepositioned at opposite ends of the top member 14 and depend downwardlyand extend perpendicularly from the bottom surface 30 of the top member14. The projections 16 and 17 each terminate in a distal end 32 that ispointed and sharpened to facilitate the insertion of the projections 16and 17 into the vertebrae V.

[0078] The staple member 12 is most effective when the interprojectiondistance I between projections 16 and 17 is at least 4.0 mm andpreferably 6.0 mm greater than the diameter of the particular spinalfusion implant 40 for which the spinal fixation device 10 is being usedso that at least 2.0 mm and preferably 3.0 mm of bone from the vertebraeV will be present between the spinal fusion implant 40 and each of theprojections 16 and 17. Typically, intervertebral spinal fusion implantshave a diameter that ranges from 12.0 mm to 28.0 mm, therefore, theinterprojection distance I typically will range from 18.0 mm to 34.0 mmfor most applications.

[0079] In the preferred embodiment, the projections 16 and 17 comprise aseries of segmented and ratcheted portions 34. The segmented andratcheted portions 34 provide for a “one way” insertion of the staplemember 12 to prevent the backing-out of the projections 16 and 17 oncethey are inserted into the bone of the vertebrae V. In the preferredembodiment, each segmented and ratcheted portion 34 of the projections16 and 17 is conical in shape and the diameter of each segmented andratcheted portion 34 increases in the direction from the distal end 32toward the top member 14 so that the projections 16 and 17 resemble astack of cones. The segmented and ratcheted portions 34 are spacedapproximately 2.0 mm to 4.0 mm apart, with 3.0 mm being the preferreddistance between each segmented and ratcheted portion 34.

[0080] Referring to FIGS. 11-12, in the preferred embodiment of thespinal fixation device 10, in order to further facilitate the insertionof the projections 16 and 17 into the vertebrae V, the distal end 32 ofeach projection 16 has an eccentric, incline-planed inner surface 36 asshown in FIG. 11. The eccentric, incline-planed inner surface 36 of eachof the projections 16 and 17 create a force F which pushes the bone ofthe vertebrae V toward the spinal fusion implant 40 as the staple member12 is inserted into each of the vertebrae V as shown in FIG. 12.

[0081] Referring to FIGS. 13A-13F, in the preferred embodiment of thespinal fixation device 10, the projections 16 and 17 are cylindrical inshape having a circular cross section as shown for projection 16 in FIG.13A. Alternatively, the projection 16 a may have a triangular crosssection as shown in FIG. 13B; the projection 16 b may have a squarecross section as shown in FIG. 13C; the projection 16 c may have arectangular cross section as shown in FIG. 13D; the projection 16 d mayhave a trapezoidal cross section as shown in FIG. 13E; or the projection16 e may have a cross section with a configuration as shown in FIG. 13F.

[0082] In the preferred embodiment, the projections 16 and 17 each havea diameter of approximately 2.0 mm to 4.0 mm, with 3.0 mm being thepreferred diameter at the widest point. The projection 16 and 17 eachhave a length ranging from 16.0 mm to 28.0 mm, with 22.0 mm being thepreferred length when the spinal fixation device 10 is implanted in thedirection of the anterior aspect of the vertebra V to the posterioraspect of the vertebrae V. Alternatively, it is appreciated that theprojections 16 and 17 each could have a longer length depending on thediameter of the vertebrae V in which the projections 16 and 17 areimplanted.

[0083] Referring again to FIG. 9, the top member 14 of the staple member12 has a central bar 35 extending from the center of its bottom surface30, for interdigitating and mating to an already implantedintervertebral spinal fusion implant 40. In the preferred embodiment,the central bar 35 has a thickness in the range of 0.5 mm to 1.5 mm,with 0.5 mm being the preferred thickness.

[0084] Referring to FIG. 1, the central bar 35 is configured so that itcomplements and engages the depression 44 at the insertion end 43 of thespinal fusion implant 40. Once engaged to the depression 44, the bar 35interdigitates with the depression 44 of the spinal fusion implant 40 tolock and prevent the rotation of the spinal fusion implant 40.

[0085] Referring to FIG. 14, in the preferred embodiment, the staplemember 12 is secured to the spinal fusion implant 40 by a screw 60having threaded end 61 with a locking thread pattern 62 and screw head64. The locking thread pattern 62 has a reduced pitch at the bottom ofthe threaded end 61 such that the screw 60 is self-locking. However, itis appreciated that the threaded pattern 62 may be any of the means forlocking a screw well known by those skilled in the art.

[0086] Referring to FIGS. 2 and 8, the threaded end 61 of the screw 60passes through the central opening 18 of the top member 14 and thethreaded pattern 62 threads into the threaded aperture 45 of the spinalfusion implant 40. The screw head 64 fits within the countersunk recess19 of the top member 14 such that the screw head 64 is at or below theplane of the upper surface 20 of the top member 14. In the preferredembodiment, the central opening 18 has a diameter ranging from 4.5 mm to5.5 mm, with 5.0 mm being the preferred diameter. The countersunk recess19 has a diameter in the range of 6.0 mm to 8.0 mm with 7.0 mm being thepreferred diameter.

[0087] Referring to FIGS. 15A, 15B, and 15C, an enlarged cross sectionalview of three different embodiments of a securing means 65 for lockingthe screw 60 once it is threaded to the spinal fusion implant 40 areshown. In FIG. 15A, the securing means 65 comprises a notch 66 in thesurface 20 of the top member 14 which is preferably made of metal. Oncethe screw 60 is threaded and securely tightened to the spinal fusionimplant 40, a chisel C is used to bend a portion 67 of the top member 14into the central opening 18 and against the screw head 64 so as toprevent the outward excursion and any unwanted loosening of the screw60.

[0088] In FIG. 15B, a second embodiment of the securing means 65 a isshown comprising a central score 66 a concentric with the centralopening 18. A screw 60 a having a slot 61 a in the screw head 64 a isthreaded and securely tightened to the spinal fusion implant 40. Aninstrument T is partially inserted into slot 61 a after which animpaction force F_(i) is applied to the instrument T to spread apart thescrew head 64 a in the direction of the arrows A so that the screw head64 a becomes deformed from the impaction force F_(i) and fits within thecentral score 66 a. Once the screw head 64 a is in the central score 66a, the outward excursion of the screw 60 a is prevented by the top lip68 of the central score 66 a.

[0089] In FIG. 15C, a third embodiment of the securing means 65 b isshown comprising a screw 60 b having a screw head 64 b with a slightlyflanged portion 69 b near the top and a slot 61 b. The central opening18 has along its circumference a recess 66 b for receiving the flangedportion 69 b of the screw head 64 b. The securing means 65 b relies onthe natural resiliency of the metal screw head 64 b such that when thescrew 60 b is being driven by a screw driver, the screw head 64 b flexesin the direction of the arrows B. In this manner, the flanged portion 69b of the screw head 64 b slides along the interior of the centralopening 18 so that the screw head 64 b is below the top lip 68 b of therecess 66 b. Once the screw driver is removed from the screw 60 b, thescrew head 64 b returns to its natural state in the direction oppositeto the arrows B so that the flanged portion 69 b is within the recess 66b. The outward excursion of the screw 60 is thus prevented by the toplip 68 b which blocks the screw head 64 b by catching the flangedportion 69 b.

[0090] FIGS. 16A-18 show the instrumentation used for installing thespinal fixation device 10. Referring to FIG. 16A, a driving instrument80 used for inserting the spinal fixation device 10 into the vertebrae Vis shown having a hollow tubular shaft 82 which terminates at one end toa bottom flat member 84 and terminates to a top flat member 86 at theother end. The bottom flat member 84 is preferably configured so that itconforms to the shape of the top member 14 of the staple member 12.

[0091] The driving instrument 80 has a pair of short posts 88 a and 88 bextending from the bottom flat member 84. The posts 88 a and 88 b areoriented on the bottom flat member 84 so as to correspond to theposition of the openings 22 a and 22 b in the upper surface 20 of thetop member 14 of the staple member 12. Each of the posts 88 a and 88 bfit into each of the openings 22 a and 22 b and keep the staple member12 aligned on the bottom flat member 84 of the driving instrument 80. Itis appreciated that the openings 22 a and 22 b in the top member 14 maybe depressions within the surface 20 of the top member 14 or may beholes that pass through the top member 14. In the preferred embodiment,the openings 22 a and 22 b gave a diameter ranging from 1.5 mm to 3.5mm, with 2.5 mm being the preferred diameter.

[0092] Referring to FIG. 16B, an alternative embodiment of the drivinginstrument 80′ which is used for inserting into the vertebrae V thespinal fixation device 210, described in detail below in reference toFIG. 26, is shown having a hollow tubular shaft 82′ which terminates atone end to a bottom flat member 84′ and terminates to a top flat member86′ at the other end. The bottom flat member 84′ is rectangular in shapeso that it conforms to the shape of the top member 214 of the spinalfixation device 210.

[0093] The driving instrument 80′ has a pair of short posts 88′a, 88′b,88′c and 88′d extending from the bottom flat member 84′. The posts88′a-88′d are oriented on the bottom flat member 84′ so as to correspondto the position of the openings 222 a-222 d of the spinal fixationdevice 210. Each of the and keep the spinal fixation device 210 alignedon the bottom flat member 84′ of the driving instrument 80′.

[0094] Referring to FIG. 17A, an alignment rod 70 comprising acylindrical shaft 72 having a smooth exterior surface 73 and a threadedend 74 may be threadably attached to the threaded aperture 45 of thespinal fusion implant 40 is shown. The alignment rod 70 fits through thecentral opening 18 of the spinal fixation device 10 and is used toproperly align the projections 16 and 17 on each side of the spinalfusion implant 40 prior to engaging the vertebrae V. Further, thealignment rod 70 also serves as a guide post for the drilling templateinstrument 50 described in greater detail below.

[0095] Referring to FIG. 17B, as an alternative embodiment of thealignment rod 70, a splined alignment rod 70′ that has a finely splinedsurface 72′ along its longitudinal axis and a threaded end 74′ that maybe attached to the threaded aperture 45 of the spinal fusion implant isshown.

[0096] Referring to FIG. 18, a drilling template instrument 50 forcreating a pair of insertion holes 53 a and 53 b in each of thevertebrae V for receiving each of the projection 16 and 17 respectivelyis shown. The drilling template instrument 50 has a template 52 with acentral aperture 54 therethrough and guide passages 55 and 56 forguiding a drill bit 51 of a drilling tool. Attached to the template 52is a handle 58 which angles away from the template 52 so as not toobstruct the line of sight of the surgeon and to allow easy access tothe template 52 and easy access to the guide holes 55 and 56 for thedrill bit 51. Extending from the center of the bottom surface of thetemplate 52 is a central member 59 (similar in structure and function tothe central bar 35) for mating to an already implanted intervertebralspinal fusion implant 40. The central member 59 interdigitates with thedepression 42 of the spinal fusion implant 40 so that the template 52 isproperly oriented about the spinal fusion implant 40 and the guide holes55 and 56 are properly oriented with respect to the vertebrae V adjacentto the spinal fusion implant 40. The alignment rod 70 serves as a guidepost for the drill template instrument 50 as it fits through the centralaperture 54 of the template 52 and aligns the template 52 with respectto the spinal fusion implant 40 and insures that it is coaxial. Thecentral aperture 54 of the drilling template instrument 50 is smooth sothat if it is placed over a splined alignment rod 70′ the drillingtemplate instrument 50 may be easily rotated about the splined alignmentrod 70′ into position such that the central member 59 is able to mateand interdigitate with the depression 44 of the spinal fusion implant40.

[0097] Referring to FIGS. 19-24, the spinal fixation device 10 of thepresent invention is inserted in the following manner: at least onespinal fusion implant 40 is surgically implanted so that it issubstantially within the disc space between two adjacent vertebrae V andengages at least a portion of each of the two adjacent vertebrae V. Oncethe spinal fusion implant 40 is in place, the alignment rod 70 isattached to the threaded aperture 45 of the spinal fusion implant 40.The alignment rod 70 serves as a guide post for the drilling templateinstrument 50 as it fits through the central aperture 54 of the template52 and aligns the template 52 coaxially with respect to the spinalfusion implant 40.

[0098] Referring to FIG. 20, once the template 52 is properly alignedand the drilling template instrument 50 is seated so that the centralmember 59 interdigitates with the spinal fusion implant 40, theinsertion holes 53 a and 53 b are drilled in each of the adjacentvertebrae V with a drilling instrument having a drill bit 51 with adiameter that is substantially smaller than the diameter of each theprojections 16 and 17 of the staple member 12.

[0099] Once the drilling of the insertion holes 53 a and 53 b iscompleted, the drill template instrument 50 is removed from the spinalfusion implant 40 and from the alignment rod 70. The alignment rod 70 isleft in place attached to the threaded aperture 45 of the spinal fusionimplant 40.

[0100] Referring to FIG. 21, the staple member 12 is placed onto thedriving instrument 80 used for driving and fixing the staple member 12into the vertebrae V so that the bottom flat member 84 and the posts 88a and 88 b are aligned with the top member 14 and the depressions 22 aand 22 b of the top member 14. The alignment rod 70 serves as a guidepost for the staple member 12 as it fits through the central opening 18of the staple member 12 and aligns the staple member 12 coaxially withrespect to the spinal fusion implant 40.

[0101] Referring to FIG. 22, once the staple member 12 is properlyplaced onto the bottom flat member 84 of the driving instrument 80, thestaple member 12 and the driving instrument 80 are aligned with respectto the alignment rod 70 so that the alignment rod 70 passes through thecentral opening 18 of the staple member 12 and is inserted into thecentral hollow portion 89 of the driving instrument 80. The staplemember 12 and the driving instrument 80 are then lowered along thealignment rod 70 so that the sharp distal end 32 of each of theprojections 16 and 17 comes into contact with the external surface ofthe vertebrae V and is aligned with the previously drilled insertionholes 53 a and 53 b.

[0102] As shown in FIG. 22A, it is preferred that the insertion holes 53a and 53 b be drilled so that when the projections 16 and 17 areinserted into the holes 53 a and 53 b, the incline planed inner surface36 of each of the projections 16 and 17 contacts the inner wall W of theinsertion holes 53 a and 53 b that is closest to the spinal fusionimplant 40. In this manner a compression force F is created as each ofthe projections 16 and 17 of the staple member 12 is inserted intoinsertion holes 53 a and 53 b, respectively, compressing the bone of thevertebrae V toward the spinal fusion implant 40.

[0103] Referring to FIG. 23, the staple member 12 is then driven intothe vertebrae V by applying a high impaction force to the drivinginstrument 80 with a hammer H or other impacting means against the topflat member 86 of the driving instrument 80. The staple member 12 isdriven into the vertebrae V such that the projections 16 and 17 aremoved forward into the insertion holes 53 a and 53 b, respectively,until the bottom surface 30 of the top member 14 of the staple member 12comes to rest against the surface of the vertebrae V.

[0104] Referring to FIGS. 23-24, the driving instrument 80 is liftedaway from the alignment rod 70 so that the alignment rod 70 is no longerwithin the central hollow portion 89 of the driving instrument 80. Thealignment rod 70 is unthreaded from the threaded aperture 45 and isremoved from the spinal fusion implant 40. The staple member 12 issecured to the spinal fusion implant 40 with the locking screw 60 whichhas a threaded pattern 62 with a reduced pitch. The reduced pitch of thelocking screw 60 locks the locking screw 60 to the spinal fusion implant40 with minimal turning of the locking screw 60 and prevents anyunwanted loosening. Further, any of the three embodiments of thesecuring means 65, 65 a or 65 b described above in reference to FIGS.15A-15C may be used to further prevent any unwanted loosening andoutward excursion of the screw 60.

[0105] Referring back to FIG. 12, once the staple member 12 is driveninto the vertebrae V and is secured to the spinal fusion implant 40, thespinal fusion implant 40 is prevented from rotating along its rotationalaxis R by its connection to the staple member 12 which is fixated acrossthe disc space between the vertebrae V. The staple member 12 isprevented from backing out from the vertebrae V along the longitudinalaxis L by its connection to the spinal fusion implant 40 and by thesegmented and ratcheted portions 34 of the projections 16 and 17. Inthis manner, the staple member 12 and the spinal fusion implant 40interact to prevent the dislodgement of each other from the vertebrae Vin which they are implanted. Thus, the staple member 12 is made safeagainst dislodgement by attachment to the spinal fusion implant 40 andthe stability of the spinal fusion implant 40 is assured as it is alsostabilized by the staple member 12 and each works in connection with theother to remove the only remaining degree of freedom that would allowfor the disengagement of either. In addition, the incline planed innersurface 36 at the distal end 32 of the projections 16 and 17 forces bonetoward the spinal fusion implant 40 along force lines F to furthersecure the spinal fusion implant 40 and further prevent the dislodgementof the spinal fusion implant 40.

[0106] It is appreciated by those skilled in the art that when the boneof the vertebrae V is sufficiently soft, a shorter method (hereinafterreferred to as the “Short Method”) of inserting the spinal fixationdevice 10 is possible by omitting the steps of drilling the insertionholes 53 a and 53 b prior to inserting the staple member 12 into thevertebrae V.

[0107] Referring to FIG. 22, in the Short Method, the splined alignmentrod 70′ that is finely splined along its longitudinal axis is usedinstead of the alignment rod 70. Once the splined alignment rod 70′ hasbeen attached to the spinal fusion implant 40, the staple member 12 maybe placed over the splined alignment rod 70′ so that the splinedalignment rod 70′ passes through the aperture 18 and into the centralaperture 89 of the driving instrument 80. The central aperture 89 of thedriving instrument 80 is correspondingly splined to the splines of thesplined alignment rod 70′ so that the staple member 12 can be alignedwith respect to the spinal implant 40. The alignment of the staplemember 12 and the driving instrument 80 is maintained as thecorresponding splines of the central aperture 89 interdigitate with thesplines of the splined alignment rod 70′ and prevent the rotation of thestaple member 12 about the splined alignment rod 70′. The prevention ofrotation about the splined alignment rod 70′ is especially importantwhen the Short Method is used to insert the spinal fixation device 10,as no insertion holes 53 a and 53 b have been drilled in the vertebraeV. The staple 12 can be driven directly into the vertebrae V by theapplication of a high impaction force to the driving instrument 80 asdescribed above and shown in FIG. 22.

[0108] Once the staple member 12 is driven into the vertebrae V, thesteps of the longer method described above are used to secure the spinalfixation device to the spinal fusion implant 40 are the same. The ShortMethod of inserting the staple member 12 reduces the amount of timerequired to insert and secure the spinal fixation device 10 of thepresent invention and thus reduces the overall duration of the spinalfixation surgical procedure.

[0109] While the present invention has been described with respect toits preferred embodiment, it is recognized that alternative embodimentsof the present invention may be devised without departing from theinventive concept.

[0110] For example, referring to FIG. 25, a first alternative embodimentof a spinal fixation device 110 having a staple member 112 with a topmember 114 generally in the shape of an elongated oval having two curvedsides 124 a and 124 b is shown. In this alternative embodiment, thecurved sides 124 a and 124 b have upper edges 125 a and 125 b,respectively, that are radiused to conform to the external curvature ofthe vertebrae V thereby creating smooth contoured surfaces as describedabove for the spinal fixation device 10, the preferred embodiment of thepresent invention. The top member 114 has openings 122 a and 122 b inthe upper surface 120 of the top member 114 and has two projections 116and 117 depending downwardly from the bottom surface 130 of the topmember 114 at opposite ends of the staple member 112. The projections116 and 117 are the same as the projections 16 described above for thepreferred embodiment.

[0111] Referring to FIG. 26, a second alternative embodiment of thespinal fixation device 210 having a staple member 212 is shown with atop member 214 that is generally rectangular in shape and has an uppersurface 220 with openings 222 a, 222 b, 222 c, and 222 d. The top member214 has four projections 216, 217, 218, and 219 depending from itsbottom surface at each of its corners. The projections 216-217 are thesame as the projections 16 and 17 described above in the preferredembodiment. The top member 214 has four straight sides 228 a, 228 b, 228c, and 228 d having upper edges 225 a, 225 b, 225 c, and 225 d,respectively, that are radiused to conform to the to external curvatureof the vertebrae V create a smooth surface as described above for thepreferred embodiment. The driving instrument 80′ shown in FIG. 16B isused to insert the spinal fixation device 210.

[0112] Referring to FIG. 27, a third alternative embodiment of thespinal fixation device 310 having a staple 312 with a top member 314that is generally triangular is shown. The top member 314 has twoprojections 316 and 317 depending from the bottom surface of the topmember 314 that engage the vertebrae V. Extending from the center of thebottom surface of the top member 314 is a central member 390 which issimilar to the central bar 35 of the preferred embodiment of the spinalfixation device 10 in that the central member 390 interdigitates withthe depression 44 of the spinal fusion implant 40. However, the centralbar 390 also has an extension arm 392 that extends laterally from thetop member 314 to span the diameter of an adjacent spinal fusion implant41. The extension arm 392 interdigitates with the depression 44 of thespinal implant 41. The extension arm 392 has a central aperture 394 forreceiving a screw 60 b used to couple the extension arm 392 to thespinal fusion implant 41. In this manner, a single spinal fixationdevice 310 is capable of interdigitating with two adjacent spinal fusionimplants 40 and 41 to lock and prevent the rotation and any excursion ofthe spinal fusion implants 40 and 41. The fixation of two spinal fusionimplants 40 and 41 is possible while leaving no protruding metal, suchas the top member 314, on the side of the spine where the vessels arelocated in close approximation to the vertebrae as is the case with theL₄ and L₅ vertebrae where the vessels are located over the left side ofthose vertebrae. It is appreciated that any of the securing means 65-65b, described above may be used to lock the screw 60 b to the extensionarm 392.

[0113] Referring to FIG. 28, a fourth alternative embodiment of thespinal fixation device 410 having a staple member 412 with a top member414 that is generally triangular in shape is shown in the installedposition. The top member 414 is wider and larger than top member 14 asit is used with an implant 440 having a large diameter in the range of22.0 mm to 28.0 mm. The top member 414 needs to be wider when used withimplant 440 in order to provide a central bar 435 of sufficient lengthto interdigitate and mate with the depression 444 of the implant 440 inorder to prevent its rotation. Further, the top member 414 is tapered atportion 416 so as not to cause erosion or pressure against the vesselsthat may be present in the area of the spine adjacent to the portion 416of the top member 414.

[0114] Referring to FIGS. 29-32, a fifth alternative embodiment of thespinal fixation device 510 with a staple member 512 having a generallyrectangular top member 514 is shown. The staple member 512 is similar instructure to the staple 212 described above except that the top member514 has multipronged projection blades 516 and 517 depending from itslower surface 530 as shown in FIG. 30. The multipronged projectionblades 516 and 517 have the same function and similar structure as theprojections 16 and 17 described above and include segmented andratcheted portions 534 which are similar in design are function tosegmented and ratcheted portions 34. The multipronged blade projections516 and 517 offer the added advantage of increasing the strength andstability of the staple member 514 once it is inserted into the bone ofthe vertebrae V providing a greater area of engagement of the staplemember 512 to the vertebrae V.

[0115] The lower surface 530 has knobs 532 and 534 extending therefromfor engaging and interdigitating with a spinal implant 540 having aninsertion end 541 with openings 542 and 544 for receiving knobs 532 and534 respectively.

[0116] Referring to FIGS. 31 and 32, the spinal fusion implant 540 isshown inserted within the disc space between two adjacent vertebrae V.The spinal implant 540 is generally rectangular in shape. The multiprongblade projections 516 and 517 have a width that is approximately equalor slightly less than the width of the spinal fusion implant 540. Onceinserted, the spinal fixation device 510 compresses the bone of thevertebrae V towards the spinal fusion implant 540 as discussed above inreference to FIG. 12. The spinal fixation device 510 may be secured tothe spinal fusion implant 540 with a screw 60 as discussed above.

[0117] The spinal fixation device 510 having a staple member 512 is thepreferred embodiment of the present invention for use with amulti-segmental spinal alignment means 600 described in greater detailbelow in that the staple 512 provides a more solid anchoring means thatcan resist greater torsion forces resulting from the application of themulti-segmental spinal alignment means 600 to align the spine.

[0118] Alternatively, for all of the embodiments described above, thespinal fixation device 10 of the present invention could be made ofresorbable materials, such as bio-compatible resorbable plastics, thatresorb at an appropriate rate such that once the spinal fixation device10 is no longer needed (i.e. when spinal fusion is complete) the bodywould resorb the spinal fixation device 10. One such resorbable materialis polygalactone, however any other resorbable plastic or other materialsafely usable within the human body are also within the scope of thepresent invention.

[0119] Further, the spinal fixation device could be only in partresorbable such that the projections 16 and 17 of the staple member 12would be non-resorbable and would remain incarcerated in the vertebrae Vand sealed off once the resorbable portion of the staple is resorbed bythe body.

[0120] Referring to FIGS. 33 and 34, as a further application, thespinal fixation device 510 of the present invention may be used as ananchor for a multi-segmental spinal alignment means 600, such that amultiplicity of spinal fixation devices may then be interconnected via acable, rod, bar, or plate, so as to achieve or maintain any desiredmulti-segment spinal alignment. In the preferred embodiment, themulti-segmental spinal alignment means 600 comprises more than onespinal fixation device 510 of the present invention placed in seriesalong the spine such that each spinal fixation device 510 spans one discD and engages two adjacent vertebrae V. The spinal fixation device 510is preferred over the other embodiments of the present invention in thatit has a greater area of engagement with the vertebrae V so as toprovide a solid anchoring means for the multi-segmental spinal alignmentmeans 600. However, it is appreciated that other embodiments includingbut not limited to those described herein may be utilized as anchoringmeans for the multi-segmental spinal alignment means 600.

[0121] When used as an anchor, each spinal fixation device 510interdigitates with and is connected to a spinal fusion implant 610having an insertion end 612, an interior chamber 614 and is inserted inthe disc space between the two adjacent vertebrae. The spinal fusionimplant 610 has a threaded blind hole 620 for receiving a threaded post622 therein. The blind hole 620 has a casing that is made of strongsurgically, implantable material such as, but not limited to titanium.The casing 624 extends from the insertion end 612 of the spinal fusionimplant 610 into the interior central chamber 614. The insertion end 612has a rigid construction that is capable of withstanding high torsionforces resulting from the tensioning of the multi-segmental spinalalignment means to align segments of the spine. In the preferredembodiment, the insertion end 612 of the spinal fusion implant has anend portion 626 that closes the insertion end 612. The end portion issubstantially thicker than the rest of the spinal fusion implant 610 andin the preferred embodiment, the end portion 626 has thickness rangingfrom 1.5 mm to 4.0 mm, with 2.5 mm being the preferred thickness.

[0122] Referring to FIG. 34, the threaded post 622 has a threaded end628 with a locking thread pattern that is substantially longer than thelocking thread pattern 62 of the screw 60 described above and a headportion 630 having a hole 632 for receiving a rod 634 or a cabletherethrough. The head portion 630 has a rounded exterior surface toprevent any damage such as aortic erosion to the vessels in the areaadjacent to the spine. In the preferred embodiment the threaded post hasa diameter ranging from 3.0 mm to 6.0 mm, with 4.5 mm being thepreferred diameter and has a length ranging from 15.0 mm to 25.0 mm,with 20.0 mm being the preferred length. The head portion 630 extends ata height above the top member 514 of the spinal fixation device 510 ofapproximately 8.0 mm to 16.0 mm, with 12.0 being the height preferredonce it is threadably attached to the spinal fusion implant 610 suchthat it does not significantly protrude from the spinal column into thetissue and vessels adjacent thereto.

[0123] Once the threaded post 622 is attached to the spinal fusionimplant 610, the head portion 630 of each threaded post 622 areconnected to one another by the rod 634 having a sufficient diameter tofit through the hole 632 of each head portion 630. The rod 634 has atleast a portion thereof that is threaded so that a plurality of locknuts 638 may be used to secure the rod 634 to the head portions 630. Thelock nuts 638 may also be used as length adjusting means to adjust thelength of the rod 634 between head portions 630 so that segmentalportions of the spine may be held closer together or held further apartfor the purposes of aligning the spine. It is appreciated that aplurality of multi-segmental spinal alignment means 600 may be placed inseries either on one side or on opposite sides of the spine, such thatone side of the spine may be extended while the other side may be heldstationary or may be compressed in order to achieve proper spinalalignment. The multi-segment spinal alignment may be maintained bykeeping the rod tensioned with the lock nuts 638 or by any other meanswell known by those skilled in the art. It is also appreciated that inplace of a rod 634 a cable, a plate or any other means well known bythose skilled in the art may be used to interconnect the multi-segmentalspinal alignment means.

[0124] Referring to FIG. 35, a sixth alternative embodiment of thespinal fixation device of the present invention is shown and generallyreferred to by the numeral 710. The spinal fixation device 710 comprisesa top member 714 that is similar to the top member 14 described above,except that it does not have projections 16 and 17 extending from thebottom surface. Like numbers are being used to designate identicalfeatures of the top members 14 and 714.

[0125] In the top member 714, instead of having projections 16 and 17,independent projection members 716 and 717 in the form of screws areused to secure the top member 714 of the spinal fixation device 710 tothe vertebrae V of the spine. The projection screw members 716 and 717each terminate in a sharp distal end 720 and 722 respectively, have athreaded portion 723, and have screw heads 724 and 726 for engaging ascrew driver or similar driving instrument.

[0126] The top member 714 has a hole 728 on one end and a hole 730 atits other end through which each of the projection screw members 716 and717 respectively, may pass. The projection screw members 716 and 717pass through the holes 728 and 730 to engage the vertebrae V. Each ofthe holes 728 and 730 has a concentric counter sunk recess 732 forreceiving and seating the screw heads 724 and 726 of the projectionscrew members 716 and 717 so that the screw heads 724 and 726 are flushor below the top surface 20 of the top member 714 once inserted into thevertebrae V.

[0127] As the projection screw members 716 and 717 are threaded, theycan be rotationally advanced into the vertebrae instead of by way of animpaction force such that the potential for damage to the vertebrae V isreduced. The threads of the threaded portion 723 follow one another asthe projection screw members 716 and 717 are being screwed into the bonesuch that the integrity of the vertebrae V is preserved. Also, as theprojection screw members 716 and 717 are independent from the top member714, the penetration depth of the spinal fixation device 710 into thebone of the vertebrae V may be easily altered by selecting differentsized projection screw members 716 and 717 appropriate for theparticular vertebrae being fused. Further, it is possible to configurethe holes 728 and 730 in the top member 714 such that the projectionscrew members 716 and 717 may be inserted into the vertebrae V from anumber of different angles relative to the top member 714.

[0128] Adjacent and proximate to each of the holes 728 and 730 arethreaded openings 740 and 742, respectively, for receiving lockingscrews 744 and 746 respectively. Each of the locking screws 744 and 746have a head portion 750 and a locking thread portion 754 for threadablyand lockably engaging the threaded openings 740 and 742. The lockingscrews 744 and 746 are attached to the top member 714 after theprojection screw members 716 and 717 have been inserted into thevertebrae V. At least a part of the head portion 750 and 752 blocks andpreferably makes contact with the screw projections 716 and 717 toprevent any unwanted loosening and outward excursion of the screwprojections 716 and 717.

[0129] It is appreciated that the projection members 716 and 717,instead of being threaded screws, may have a number of otherconfigurations such as, but not limited to, the configurations of theprojections described above for the various embodiments of the presentinvention. If the projections members 716 and 717 are ratcheted insteadof being threaded, they can be driven into the vertebrae V with adriving instrument and impaction force as described above for the methodof the present invention.

[0130] While the present invention has been described with respect toits preferred embodiment and a number of alternative embodiments, it isrecognized that additional variations of the present invention may bedevised without departing from the inventive concept and scope of thepresent invention.

I claim:
 1. An apparatus for stabilizing vertebral bodies adjacent adisc space of a human spine, said apparatus comprising: an interbodyspinal fusion implant adapted to be surgically implanted at least inpart within the disc space between the adjacent vertebral bodies in asegment of the spine, said implant comprising upper and lower portionsfor contacting each of the adjacent vertebral bodies when positionedtherein, each of said upper and lower portions having at least oneopening adapted to communicate with one of the adjacent vertebralbodies, said openings of said upper and lower portions being incommunication with one another and adapted for permitting for the growthof bone from adjacent vertebral body to adjacent vertebral body throughsaid implant, said implant having an insertion end for entry into thespine and a trailing end opposite said insertion end; and a spinalfixation device coupled to said trailing end of said spinal implant andadapted to be attached to each of the adjacent vertebral bodies, saidspinal fixation device having a length sufficient to span the disc spaceand connect to each of the vertebral bodies adjacent to the disc space.2. The apparatus of claim 1, wherein said spinal fixation devicecomprises at least a first opening formed therethrough to receive afirst fastener to secure said spinal fixation device to one of thevertebral bodies and at least a second opening formed therethrough toreceive a second fastener to secure said spinal fixation device toanother one of the vertebral bodies.
 3. The apparatus of claim 1,further comprising at least one opening adapted to receive a fastener tosecure said spinal fixation device to said spinal implant.
 4. Theapparatus of claim 1, wherein said spinal fixation device has a topmember having a longitudinal axis and a horizontal axis transverse tothe longitudinal axis, said top member having a plurality of openingstherethrough, at least a first pair of said openings being aligned alongthe longitudinal axis and at least a second pair of said openings beingaligned along the horizontal axis.
 5. The apparatus of claim 4, whereinsaid first pair of openings are adapted to receive a fastener forsecuring said spinal fixation device to the vertebral bodies.
 6. Theapparatus of claim 4, wherein said second pair of openings are adaptedto receive a fastener for securing said spinal fixation device to saidspinal implant.
 7. The apparatus of claim 1, wherein said spinalfixation device comprises at least two fasteners for attaching saidspinal fixation device to each of the adjacent vertebral bodies.
 8. Theapparatus of claim 7, wherein said fasteners include at least one of ascrew and a prong.
 9. The apparatus of claim 1, wherein said spinalfixation device has a top member having a lower facing portion adaptedto face said spinal implant and the vertebral bodies and an upper facingportion opposite said lower facing portion.
 10. The apparatus of claim9, wherein said lower facing portion has a first end portion forcontacting one of the adjacent vertebral bodies, a second end portionadapted to contact another of the adjacent vertebral bodies, and amiddle portion between said first and second end portions for contactingsaid spinal implant, said middle portion being at least in part in afirst plane and said first and second portions being at least in part ina second plane different than said first plane.
 11. The apparatus ofclaim 10, wherein said middle portion protrudes from said lower facingportion of said top member to form a leading wall and opposite sidewalls, said opposite side walls being at an angle to said first andsecond end portions of said lower facing portion.
 12. The apparatus ofclaim 11, wherein said opposite side walls are generally perpendicularto said first and second end portions of said lower facing portion. 13.The apparatus of claim 1, wherein said spinal fixation device isgenerally triangular in shape.
 14. The apparatus of claim 1, whereinapproximately one half of said spinal fixation device is generallytriangular in shape.
 15. The apparatus of claim 1, wherein said spinalfixation device has a opposite ends, opposite sides, and a longitudinalaxis passing through said ends, said opposite sides proximate amid-point between said opposite ends being spaced apart a greaterdistance than proximate said opposite ends.
 16. The apparatus of claim15, wherein said opposite sides are tapered toward each other proximatesaid opposite ends.
 17. The apparatus of claim 1, wherein at least aportion of said upper and lower portions of said spinal implant arearcuate along at least a portion of their length.
 18. The apparatus ofclaim 1, wherein said upper and lower portions of said spinal implantfurther comprise a protrusion for engaging the adjacent vertebralbodies.
 19. The apparatus of claim 18, wherein said protrusion is athread.
 20. The apparatus of claim 1, wherein said implant has a hollowinterior, at least one of said insertion and trailing ends of saidspinal implant is being open for loading bone growth promoting materialinto said hollow interior.
 21. The apparatus of claim 20, furthercomprising an end cap for closing said open end.
 22. The apparatus ofclaim 20, wherein said hollow interior is a chamber and the bone growthpromoting material includes a bone graft.
 23. The apparatus of claim 1,wherein said spinal implant includes an artificial material other thanbone.
 24. The apparatus of claim 1, wherein said implant comprisesharvested bone.
 25. The apparatus of claim 1, wherein said implant is incombination with bone growth promoting material.
 26. The apparatus ofclaim 25, wherein said bone growth promoting material includes at leastone of hydroxyapatite and bone morphogenetic protein.
 27. The apparatusof claim 1, wherein said implant is treated with a bone growth promotingsubstance.
 28. The apparatus of claim 1, wherein said implant is asource of osteogenesis.
 29. The apparatus of claim 1, wherein saidimplant is at least in part bioabsorbable.
 30. The apparatus of claim 1,wherein said implant comprises metal.
 31. The apparatus of claim 1,wherein said implant comprises a plastic material.
 32. The apparatus ofclaim 1, wherein said implant comprises a ceramic material.
 33. Theapparatus of claim 1, wherein said implant is formed of a porousmaterial.
 34. The apparatus of claim 1, wherein said implant is formedof a material that intrinsically participates in the growth of bone fromadjacent vertebral body to adjacent vertebral body through said implant.35. The apparatus of claim 1, wherein said implant is in combinationwith harvested bone.
 36. An apparatus for replacing a portion of ananterior longitudinal ligament that has been at least in part surgicallyremoved to access a disc space between two adjacent vertebral bodies ofa human spine, said apparatus comprising: an interbody spinal fusionimplant adapted to be surgically implanted at least in part within thedisc space between the two adjacent vertebral bodies in a segment of thespine, said implant comprising upper and lower portions for contactingeach of the adjacent vertebral bodies when positioned therein, each ofsaid upper and lower portions having at least one opening adapted tocommunicate with one of the adjacent vertebral bodies, said openings ofsaid upper and lower portions being in communication with one anotherand adapted for permitting for the growth of bone from adjacentvertebral body to adjacent vertebral body through said implant, saidimplant having an insertion end for entry into the spine and a trailingend opposite said insertion end; and an anterior longitudinal ligamentreplacement member coupled to said trailing end of said spinal implantand adapted to be attached to each of the two adjacent vertebral bodies,said ligament replacement member having a length sufficient to span thedisc space and connect to each of the vertebral bodies adjacent to thedisc space to replace at least a portion of the removed anteriorlongitudinal ligament.
 37. The apparatus of claim 36, wherein saidligament replacement member comprises at least a first opening formedtherethrough to receive a first fastener to secure said ligamentreplacement member to one of the vertebral bodies and at least a secondopening formed therethrough to receive a second fastener to secure saidligament replacement member to another one of the vertebral bodies. 38.The apparatus of claim 36, further comprising at least one openingadapted to receive a fastener to secure said ligament replacement memberto said spinal implant.
 39. The apparatus of claim 36, wherein saidligament replacement member has a top member having a longitudinal axisand a horizontal axis transverse to the longitudinal axis, said topmember having a plurality of openings therethrough, at least a firstpair of said openings being aligned along the longitudinal axis and atleast a second pair of said openings being aligned along the horizontalaxis.
 40. The apparatus of claim 39, wherein said first pair of openingsare adapted to receive a fastener for securing said ligament replacementmember to the vertebral bodies.
 41. The apparatus of claim 39, whereinsaid second pair of openings are adapted to receive a fastener forsecuring said ligament replacement member to said spinal implant. 42.The apparatus of claim 36, wherein said ligament replacement membercomprises at least two fasteners for attaching said ligament replacementmember to each of the adjacent vertebral bodies.
 43. The apparatus ofclaim 42, wherein said fasteners include at least one of a screw and aprong.
 44. The apparatus of claim 36, wherein said ligament replacementmember has a top member having a lower facing portion adapted to facesaid spinal implant and the vertebral bodies and an upper facing portionopposite said lower facing portion.
 45. The apparatus of claim 44,wherein said lower facing portion has a first end portion for contactingone of the adjacent vertebral bodies, a second end portion adapted tocontact another of the adjacent vertebral bodies, and a middle portionbetween said first and second end portions for contacting said spinalimplant, said middle portion being at least in part in a first plane andsaid first and second portions being at least in part in a second planedifferent than said first plane.
 46. The apparatus of claim 45, whereinsaid middle portion protrudes from said lower facing portion of said topmember to form a leading wall and opposite side walls, said oppositeside walls being at an angle to said first and second end portions ofsaid lower facing portion.
 47. The apparatus of claim 46, wherein saidopposite side walls are generally perpendicular to said first and secondend portions of said lower facing portion.
 48. The apparatus of claim36, wherein said ligament replacement member is generally triangular inshape.
 49. The apparatus of claim 36, wherein approximately one half ofsaid ligament replacement member is generally triangular in shape. 50.The apparatus of claim 36, wherein said ligament replacement member hasa opposite ends, opposite sides, and a longitudinal axis passing throughsaid ends, said opposite sides proximate a mid-point between saidopposite ends being spaced apart a greater distance than proximate saidopposite ends.
 51. The apparatus of claim 50, wherein said oppositesides are tapered toward each other proximate said opposite ends. 52.The apparatus of claim 36, wherein at least a portion of said upper andlower portions of said spinal implant are arcuate along at least aportion of their length.
 53. The apparatus of claim 36, wherein saidupper and lower portions of said spinal implant further comprise aprotrusion for engaging the adjacent vertebral bodies.
 54. The apparatusof claim 53, wherein said protrusion is a thread.
 55. The apparatus ofclaim 36, wherein said implant has a hollow interior, at least one ofsaid insertion and trailing ends of said spinal implant is being openfor loading bone growth promoting material into said hollow interior.56. The apparatus of claim 55, further comprising an end cap for closingsaid open end.
 57. The apparatus of claim 55, wherein said hollowinterior is a chamber and the bone growth promoting material includes abone graft.
 58. The apparatus of claim 36, wherein said spinal implantincludes an artificial material other than bone.
 59. The apparatus ofclaim 36, wherein said implant comprises harvested bone.
 60. Theapparatus of claim 36, wherein said implant is in combination with bonegrowth promoting material.
 61. The apparatus of claim 60, wherein saidbone growth promoting material includes at least one of hydroxyapatiteand bone morphogenetic protein.
 62. The apparatus of claim 36, whereinsaid implant is treated with a bone growth promoting substance.
 63. Theapparatus of claim 36, wherein said implant is a source of osteogenesis.64. The apparatus of claim 36, wherein said implant is at least in partbioabsorbable.
 65. The apparatus of claim 36, wherein said implantcomprises metal.
 66. The apparatus of claim 36, wherein said implantcomprises a plastic material.
 67. The apparatus of claim 36, whereinsaid implant comprises a ceramic material.
 68. The apparatus of claim36, wherein said implant is formed of a porous material.
 69. Theapparatus of claim 36, wherein said implant is formed of a material thatintrinsically participates in the growth of bone from adjacent vertebralbody to adjacent vertebral body through said implant.
 70. The apparatusof claim 36, wherein said implant is in combination with harvested bone.71. A method for stabilizing two vertebral bodies adjacent a disc spaceof a human spine, comprising the steps of: removing at least a portionof an anterior longitudinal ligament of a segment of the human spine toaccess the disc space; forming an implantation space across the discspace and into a portion of the adjacent vertebral bodies; implanting aninterbody spinal implant adapted to be surgically implanted at least inpart within the implantation space, the spinal implant being adapted tocontact both of the vertebral bodies adjacent to the disc space when thedisc space has been restored to approximate a normal height for the discspace; and replacing the removed portion of the anterior longitudinalligament by attaching an anterior longitudinal ligament replacementmember to each of the two adjacent vertebral bodies, the ligamentreplacement member being coupled to the spinal implant, the ligamentreplacement member having a length sufficient to span the disc space andto contact each of the two adjacent vertebral bodies and the spinalimplant.
 72. The method of claim 71, further comprising the step ofusing at least a first fastener to secure the ligament replacementmember to one of the vertebral bodies and at least a second fastener tosecure said ligament replacement member to another one of the vertebralbodies.
 73. The method of claim 71, further comprising the step of usinga fastener to secure said ligament replacement member to said spinalimplant.
 74. The method of claim 72, wherein said fasteners include atleast one of a screw and a prong.
 75. The method of claim 71, whereinsaid implanting step includes implanting the spinal implant having atleast a portion of the upper and lower portions being arcuate along atleast a portion of their length.
 76. The method of claim 71, whereinsaid implanting step includes implanting the spinal implant having upperand lower portions comprising a protrusion for engaging the adjacentvertebral bodies.
 77. The method of claim 76, wherein said protrusion isa thread.
 78. The method of claim 71, wherein said implanting stepincludes implanting the spinal implant in combination with harvestedbone.
 79. The method of claim 71, wherein said implanting step includesimplanting the spinal implant in combination with bone growth promotingmaterial.
 80. The method of claim 79, wherein said bone growth promotingmaterial includes at least one of hydroxyapatite and bone morphogeneticprotein.
 81. A spinal system comprising: a first implant including afirst body portion positionable in a disc space between adjacent upperand lower vertebral bodies; a second implant including a second bodyportion positionable in the disc space between adjacent upper and lowervertebral bodies; and a ligament replacement member extending from eachof said first body portion and said second body portion and positionablealong the upper vertebral body and along the lower vertebral body whensaid first body portion and said second body portion are positioned inthe disc space.
 82. The system of claim 81, wherein said first bodyportion has a leading end and an opposite trailing end, and saidligament replacement member is attached to said trailing end of saidfirst body portion.
 83. The system of claim 81, wherein each of saidfirst and second body portions includes an upper bearing surface and alower bearing surface separated by a height, said height adapted tomaintain spacing between the adjacent vertebral bodies.
 84. The systemof claim 83, wherein each of said upper and lower bearing surfaces ofeach of said first and second body portions includes a bone engagingsurface to inhibit expulsion of said implant from the disc space. 85.The system of claim 84, wherein each of said first and second bodyportions is configured for rotatable insertion into the disc space andeach of said bone engaging surfaces is threaded.
 86. The system of claim81, wherein at least one of said first and second body portions isshaped for push-in insertion into the disc space.
 87. The system ofclaim 81, wherein said first and second implants are spinal fusiondevices.
 88. The system of claim 81, wherein said ligament replacementmember comprises: a first opening formed therethrough to receive a firstfastener to secure the ligament replacement member to the uppervertebral body; and a second opening formed therethrough to receive asecond fastener to secure the ligament replacement member to the lowervertebral body.
 89. The system of claim 81, wherein said ligamentreplacement member is removably attachable to at least one of said firstand second body portions.